JP5292995B2 - Motor control device and electric power steering device - Google Patents

Motor control device and electric power steering device Download PDF

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JP5292995B2
JP5292995B2 JP2008214393A JP2008214393A JP5292995B2 JP 5292995 B2 JP5292995 B2 JP 5292995B2 JP 2008214393 A JP2008214393 A JP 2008214393A JP 2008214393 A JP2008214393 A JP 2008214393A JP 5292995 B2 JP5292995 B2 JP 5292995B2
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command value
motor control
current command
voltage
axis current
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JP2010051125A (en
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浩 鈴木
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株式会社ジェイテクト
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B62LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62DMOTOR VEHICLES; TRAILERS
    • B62D5/00Power-assisted or power-driven steering
    • B62D5/04Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/046Controlling the motor
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B62LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62DMOTOR VEHICLES; TRAILERS
    • B62D5/00Power-assisted or power-driven steering
    • B62D5/04Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/0481Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/05Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation specially adapted for damping motor oscillations, e.g. for reducing hunting
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/06Rotor flux based control involving the use of rotor position or rotor speed sensors
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2205/00Indexing scheme relating to controlling arrangements characterised by the control loops
    • H02P2205/05Torque loop, i.e. comparison of the motor torque with a torque reference
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02PCONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2207/00Indexing scheme relating to controlling arrangements characterised by the type of motor
    • H02P2207/05Synchronous machines, e.g. with permanent magnets or DC excitation

Description

  The present invention relates to a motor control device and an electric power steering device.

  Conventionally, in applications where smooth motor rotation and high quietness are required, such as an electric power steering device (EPS), a brushless motor is often used as the drive source. The motor control is generally configured such that sine wave energization is performed for each phase (U, V, W) based on current control in the d / q coordinate system.

  By the way, in the motor control device having such a configuration, when there is an upper limit to the output voltage, the required output voltage can be applied to the drive circuit at the maximum voltage (for example, the power supply voltage) when the motor rotates at high speed. So-called voltage saturation may occur, which may cause torque ripple and noise.

  Therefore, conventionally, a voltage limiting process (voltage saturation guard) is performed for suppressing the occurrence of the voltage saturation by limiting the voltage command value. For example, the limit value in the voltage limiting process is determined in advance based on the standards and specifications of the drive circuit and the like. As shown in FIG. 9, when the combined vector Vdq * of the d-axis voltage command value Vd * and the q-axis voltage command value Vq * exceeds the preset voltage limit value Vdq_lim, that is, at the time of voltage saturation, The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are corrected so that the corrected combined vector Vdq * is equal to or less than the voltage limit value Vdq_lim.

  In the example shown in FIG. 9, the q-axis voltage command value Vq * is reduced while the d-axis voltage command value Vd * is maintained. In addition, the angle of the combined vector Vdq * is maintained after the voltage saturation. In some cases, a configuration that corrects the d-axis voltage command value Vd * and the q-axis voltage command value Vq * is adopted (see, for example, Patent Document 1).

Such a voltage saturation problem can also be dealt with by expanding the rotation region of the motor by executing field weakening control. For example, Patent Document 2 proposes a motor control device (steering device) that activates field weakening control based on a q-axis current deviation. Furthermore, the motor control device described in Patent Document 3 calculates a voltage saturation rate indicating the degree of voltage saturation based on a voltage command value calculated by executing current control. The phase of the current command value is corrected in accordance with the voltage saturation rate, and the current command value is reduced together with the field weakening to effectively prevent voltage saturation.
Japanese Patent Application Laid-Open No. 6-1553569 Japanese Patent Laid-Open No. 2003-40128 JP 2006-129632 A

  However, the q-axis voltage command value Vq * is changed to the d-axis voltage command value Vd * in the high-speed / high-torque region (voltage saturation region) in which voltage saturation occurs by executing the voltage limiting process as described above. It will vary depending on the situation. Therefore, the change in the d / q axis current is likely to be amplified, and the fluctuation may cause torque ripple and noise. Further, in the configuration in which field weakening control is activated based on the q-axis current deviation as in the conventional example of Patent Document 2, the voltage saturation state is often already at the stage where the deviation reaches the threshold, and the activation is delayed. There is a problem that is likely to occur. This delay in activation is the same as that in the conventional example of Patent Document 3 using the voltage command value calculated based on the current deviation as the basis of the field weakening control activation. In this respect, there is still room for improvement. Was supposed to leave.

  The present invention has been made to solve the above-described problems, and its object is to provide a motor control capable of realizing smooth motor rotation without causing torque ripple and noise even in a voltage saturation region. It is providing a device and an electric power steering device.

  In order to solve the above problems, the invention according to claim 1 is directed to motor control signal generation means for generating a motor control signal by executing current control in a d / q coordinate system, and a motor based on the motor control signal. And a drive circuit for outputting three-phase drive power, wherein the motor control signal generating means is based on a rotational angular velocity of the motor and a current command value of the d / q coordinate system. Estimating an expected voltage utilization rate, which is a ratio of a required output voltage to a maximum voltage that can be applied to the drive circuit, and preventing the estimated expected voltage utilization rate from exceeding a predetermined value corresponding to a voltage saturation limit. The gist is to correct the command value.

  According to the above configuration, it is possible to prevent voltage saturation from occurring. As a result, it is possible to always control the motor current without performing the voltage limiting process, and as a result, it is possible to effectively suppress the generation of torque ripple and noise. Furthermore, by estimating the expected voltage utilization rate based on the current command value before the current control is executed, the influence of the deviation between the current command and the actual current in the current control is eliminated, and the transient state leading to the voltage saturation. The generation of the voltage saturation can be suppressed promptly.

  According to a second aspect of the present invention, the motor control signal generating means calculates a d-axis current command value so as to execute field-weakening control so that the estimated expected voltage utilization rate does not exceed the predetermined value. When the estimated expected voltage utilization rate exceeds a limit value that can be handled by the field weakening control, the expected voltage utilization rate does not exceed the predetermined value by reducing the q-axis current command value. The gist is to make the above correction.

  According to the above configuration, the occurrence of voltage saturation can be prevented in a wider area. Moreover, after the expected voltage utilization rate reaches a limit value that can be handled by field-weakening control, the output performance can be maximized by using the current command value reduction control together. That is, in applications such as an electric power steering device, improvement of basic performance is the most important issue as well as reduction of vibration and noise. By adopting the above configuration and making the best use of the output performance of the motor that is the drive source, it is possible to achieve both high basic performance and quietness.

The gist of the invention described in claim 3 is that the motor control signal generating means reduces the q-axis current command value so that the estimated expected voltage utilization rate does not exceed the predetermined value.
According to a fourth aspect of the present invention, the motor control signal generating means calculates a d-axis current command value so as to execute field-weakening control so that the estimated expected voltage utilization rate does not exceed the predetermined value. Is the gist.

  According to each of the above configurations, the occurrence of voltage saturation can be prevented in advance, thereby making it possible to always control the motor current without performing voltage limiting processing. As a result, generation of torque ripple and noise can be effectively suppressed. In particular, by performing field-weakening control according to the invention described in claim 4, it is possible to avoid a decrease in torque associated with a decrease in the current command value, thereby maintaining high output performance even in the voltage saturation region. .

The gist of the invention described in claim 5 is an electric power steering device provided with the motor control device according to any one of claims 1 to 4.
According to the above configuration, it is possible to provide an electric power steering device capable of realizing smooth motor rotation without causing torque ripple or noise even in a voltage saturation region.

  According to the present invention, it is possible to provide a motor control device and an electric power steering device capable of realizing smooth motor rotation without causing torque ripple and noise even in a voltage saturation region.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in an electric power steering apparatus (EPS) will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of the EPS 1 of the present embodiment. As shown in the figure, a steering shaft 3 to which a steering wheel (steering) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4. It is converted into a reciprocating linear motion of the rack 5 by the and pinion mechanism 4. The rudder angle of the steered wheels 6 is changed by the reciprocating linear motion of the rack 5.

  Further, the EPS 1 includes an EPS actuator 10 as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system, and an ECU 11 as a control unit that controls the operation of the EPS actuator 10. .

  The EPS actuator 10 of the present embodiment is a so-called rack-type EPS actuator in which a motor 12 that is a driving source thereof is arranged coaxially with the rack 5, and an assist torque generated by the motor 12 is a ball screw mechanism (not shown). Is transmitted to the rack 5 via. In addition, the motor 12 of this embodiment is a brushless motor, and rotates by receiving supply of three-phase (U, V, W) driving power from the ECU 11. And ECU11 as a motor control apparatus controls the assist force given to a steering system by controlling the assist torque which this motor 12 generate | occur | produces (power assist control).

  In the present embodiment, a torque sensor 14 and a vehicle speed sensor 15 are connected to the ECU 11. Then, the ECU 11 executes the operation of the EPS actuator 10, that is, power assist control, based on the steering torque τ and the vehicle speed V detected by the torque sensor 14 and the vehicle speed sensor 15, respectively.

Next, the electrical configuration of the EPS of this embodiment will be described.
FIG. 2 is a control block diagram of the EPS of this embodiment. As shown in the figure, the ECU 11 includes a microcomputer 17 as motor control signal output means for outputting a motor control signal, and a drive circuit 18 for supplying three-phase drive power to the motor 12 based on the motor control signal. ing.

  The drive circuit 18 of this embodiment is a known PWM inverter in which three arms corresponding to each phase are connected in parallel with a pair of switching elements connected in series as a basic unit (arm). The motor control signal to be defined defines the on-duty ratio of each switching element constituting the drive circuit 18. A motor control signal is applied to the gate terminal of each switching element, and each switching element is turned on / off in response to the motor control signal, whereby three phases (U, V, W) is generated and output to the motor 12.

  In the present embodiment, the ECU 11 includes a current sensor 20u, 20v, 20w for detecting each phase current value Iu, Iv, Iw energized to the motor 12, and a rotation for detecting the rotation angle θ of the motor 12. An angle sensor 21 is connected. Then, the microcomputer 17 sends a motor to the drive circuit 18 based on the phase current values Iu, Iv, Iw and the rotation angle θ of the motor 12 detected based on the output signals of these sensors, and the steering torque τ and the vehicle speed V. Output a control signal.

Each control block in the microcomputer 17 described below is realized by a computer program executed by the microcomputer 17.
More specifically, the microcomputer 17 generates a current command value calculation unit 22 that calculates a current command value as a control target amount of assist force applied to the steering system, and a motor control signal for controlling the operation of the drive circuit 18. And a motor control signal generator 23 as a motor control signal generator.

  The current command value calculation unit 22 of this embodiment has a q-axis current command value calculation unit 24, and the q-axis current command value calculation unit 24 is the steering detected by the torque sensor 14 and the vehicle speed sensor 15. Based on the torque τ and the vehicle speed V, a q-axis current command value Iq * in the d / q coordinate system is calculated. Then, the current command value calculation unit 22 outputs the q-axis current command value Iq ** to the motor control signal generation unit 23 after the q-axis current command value Iq * is subjected to correction processing described later.

  The motor control signal generator 23 has the q-axis current command value Iq ** output from the current command value calculator 22 and the phase current values Iu, Iv, Iw detected by the current sensors 20u, 20v, 20w, The rotation angle θ detected by the rotation angle sensor 21 is input. In the present embodiment, “Id * = 0” is used as the d-axis current command value Id *. Then, the motor control signal generator 23 executes current feedback control in the d / q coordinate system based on the phase current values Iu, Iv, Iw and the rotation angle θ (electrical angle), thereby performing the motor control signal. Is generated.

  That is, in the motor control signal generation unit 23, the phase current values Iu, Iv, and Iw are input to the three-phase / two-phase conversion unit 25 together with the rotation angle θ, and the three-phase / two-phase conversion unit 25 performs d / q It is converted into a d-axis current value Id and a q-axis current value Iq in the coordinate system. The q-axis current command value Iq ** input to the motor control signal generator 23 is input to the subtractor 26q together with the q-axis current value Iq, and the d-axis current command value Id * is the d-axis current value Id. At the same time, it is input to the subtractor 26d. The d-axis current deviation ΔId and q-axis current deviation ΔIq calculated in the subtractors 26d and 26q are input to the corresponding F / B control units 27d and 27q, respectively. In each of these F / B control units 27d and 27q, the d-axis current command value Id * and the q-axis current command value Iq ** that are the control target values are added to the d-axis current value Id and the q-axis current that are actual currents. Feedback control for following the value Iq is performed. Specifically, the F / B control units 27d and 27q multiply the input d-axis current deviation ΔId and q-axis current deviation ΔIq by a predetermined F / B gain (PI gain) to obtain a d-axis voltage command value. Vd * and q-axis voltage command value Vq * are calculated. These d-axis voltage command value Vd * and q-axis voltage command value Vq * are input to the two-phase / three-phase converter 29 together with the rotation angle θ, and the two-phase / three-phase converter 29 receives the three-phase voltage command values. Converted to Vu *, Vv *, Vw *.

  The voltage command values Vu *, Vv *, and Vw * calculated in the two-phase / three-phase conversion unit 29 are input to the PWM conversion unit 30. In the PWM conversion unit 30, the voltage command values Vu *, Vv Duty command values corresponding to * and Vw * are generated. The motor control signal generator 23 generates a motor control signal having an on-duty ratio indicated by each duty command value, and the microcomputer 17 outputs the motor control signal to each switching element ( Output to the gate terminal), the operation of the drive circuit 18, that is, the supply of drive power to the motor 12 is controlled.

(Voltage saturation prevention control)
Next, the mode of voltage saturation prevention control in this embodiment will be described.
As shown in FIG. 2, the current command value calculation unit 22 of the present embodiment includes a q-axis current for performing a correction process on the q-axis current command value Iq * calculated by the q-axis current command value calculation unit 24. A command value correction calculation unit 31 is provided. And in this embodiment, it has the structure which prevents generation | occurrence | production of the above voltage saturation by the correction process in this q-axis current command value correction | amendment calculating part 31. FIG.

  More specifically, the current command value calculation unit 22 of this embodiment calculates (estimates) an expected voltage utilization rate that calculates (estimates) an expected voltage utilization rate f that is a ratio of the required output voltage to the maximum voltage Vmax that can be applied to the drive circuit 18. The unit 32 is provided. Then, the q-axis current command value correction calculation unit 31 corrects the q-axis current command value Iq * based on the expected voltage usage rate f estimated by the expected voltage usage rate calculation unit 32.

  More specifically, the expected voltage utilization rate calculator 32 of this embodiment receives the rotational angular velocity (electrical angular velocity) ω of the motor 12 and the q-axis current command value Iq *. In addition, since the maximum voltage Vmax that can be applied to the drive circuit 18 of the present embodiment is the power supply voltage Vb, the expected voltage utilization rate calculation unit 32 is connected to the power supply line between the drive circuit 18 and the battery 19. The power supply voltage Vb detected by the voltage sensor 33 provided is input. Then, the expected voltage utilization rate calculation unit 32 estimates the expected voltage utilization rate f based on the rotational angular velocity ω, the q-axis current command value Iq *, and the power supply voltage Vb (maximum voltage Vmax).

  Specifically, the expected voltage utilization factor calculation unit 32 of the present embodiment performs an estimation calculation of the expected voltage utilization factor f based on the following equation (1).

In the above equation (1), “L” is inductance (converted to d / q axis), “R” is motor resistance (converted to d / q axis), “Φ” is the maximum value of flux linkage, “φ” In this case, it is a constant represented by the equation “Φ = √ (3/2) × φ”.

  That is, the d-axis current command value Id * is “Id * = 0”, and the q-axis current command value Iq * is assumed to be small in time variation, and at low load / low speed rotation (normal time). The voltage equations shown in the following equations (2) and (3) are established.

Furthermore, when the amplitude of each phase voltage after conversion to the three-phase coordinate system is “Va” when controlled in the d / q coordinate system based on this voltage equation, the maximum voltage that can be output by the drive circuit 18 is If the maximum voltage Vmax that can be applied to the drive circuit 18 is satisfied, it is necessary to satisfy the relationship expressed by the following equation (4) in order to execute the sine wave energization.

Therefore, the expected voltage utilization factor f can be defined as the following equation (5). By substituting the above equations (2) and (3) into this equation (5), the above equation (1) It is possible to derive an estimation calculation formula for the expected voltage utilization factor f shown in FIG.

In addition, the q-axis current command value correction calculation unit 31 of the present embodiment corresponds to the voltage saturation limit at which the expected voltage usage rate f estimated by the expected voltage usage rate calculation unit 32 shifts to the voltage saturation state. It is determined whether or not a predetermined value f0 is exceeded. In the present embodiment, a value in the vicinity of “1” (f0 ≦ 1) is set as the predetermined value f0. If the estimated expected voltage utilization rate f exceeds a predetermined value f0 (f> f0), a new q-axis current command value Iq ** is calculated based on the following equations (6) and (7). Thus, the q-axis current command value Iq * calculated by the current command value calculation unit 22 is corrected (updated).

That is, these equations (6) and (7) can be obtained by substituting “f0” into “f” in the above equation (1) and further solving for the q-axis current command value Iq * (Iq **). it can. Then, by performing current control based on the new q-axis current command value Iq ** obtained thereby, the expected voltage utilization factor f can be suppressed to a predetermined value f0 or less.

  In this embodiment, the voltage saturation is generated by executing the correction of the q-axis current command value Iq * based on the equations (6) and (7), that is, the correction for reducing the q-axis current command value Iq *. It is the composition which prevents.

Next, a processing procedure of voltage saturation prevention control of the present embodiment configured as described above will be described.
As shown in the flowchart of FIG. 3, when the microcomputer 17 of this embodiment acquires each state quantity (step 101), it first calculates the q-axis current command value Iq * (step 102). Next, the microcomputer 17 calculates the expected voltage utilization rate f based on the above equation (1) (step 103), and the estimated expected voltage utilization rate f exceeds a predetermined value f0 corresponding to the voltage saturation limit. Whether or not (step 104). When the expected voltage utilization rate f exceeds the predetermined value f0 (f> f0, step 104: YES), a new q-axis current command value Iq ** is calculated based on the above equations (6) and (7). Thus, the correction process (update) of the q-axis current command value Iq * calculated in the above step 102 is executed (step 105).

  In step 104, when the estimated expected voltage utilization rate f does not exceed the predetermined value f0 (f ≦ f0, step 104: NO), such a new q-axis current command value Iq ** Correction processing (updating) by the above calculation is not performed (Iq ** = Iq *, step 106).

  The microcomputer 17 of the present embodiment is configured to execute the current control in the d / q coordinate system as described above based on the q-axis current command value Iq ** after the correction process (step 107). ).

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) Estimating the expected voltage utilization factor f, which is the ratio of the required output voltage to the maximum voltage Vmax that can be applied to the drive circuit 18, so that the expected voltage utilization factor f does not exceed a predetermined value corresponding to the voltage saturation limit. By correcting the q-axis current command value Iq *, it is possible to prevent the occurrence of voltage saturation. As a result, it is possible to always control the motor current without performing the voltage limiting process, and as a result, it is possible to effectively suppress the generation of torque ripple and noise.

  (2) Further, by estimating the expected voltage utilization factor f based on the q-axis current command value Iq * before execution of current control, the deviation between the current command (Iq *) and the actual current (Iq) in the current control is estimated. It is possible to suppress the occurrence of the voltage saturation promptly from the transient stage leading to the voltage saturation by eliminating the influence.

(Second Embodiment)
Hereinafter, a second embodiment in which the present invention is embodied in an electric power steering device (EPS) will be described with reference to the drawings.

  The main difference between the present embodiment and the first embodiment is only the configuration of the current command value calculation unit and the mode of voltage saturation prevention control. For this reason, for convenience of explanation, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof is omitted.

  As shown in FIG. 4, in the current command value calculation unit 42 of the present embodiment, a d-axis current command value is used instead of the q-axis current command value correction calculation unit 31 (see FIG. 2) in the first embodiment. A d-axis current command value calculation unit 43 that performs the calculation of Id * is provided, and the expected voltage usage rate f estimated by the expected voltage usage rate calculation unit 32 is input to the d-axis current command value calculation unit 43. . When the estimated expected voltage utilization factor f exceeds a predetermined value f0 corresponding to the voltage saturation limit (f> f0), the d-axis current command value calculation unit 43 executes the field weakening control. The d-axis current command value Id * is calculated, that is, the field weakening current is calculated to suppress the occurrence of voltage saturation.

  Specifically, the d-axis current command value calculation unit 43 of the present embodiment calculates a field weakening current (d-axis current command value Id *) based on the following equation (8).

That is, the voltage equation in consideration of the d-axis current is expressed by the following equations (9) and (10).

The expected voltage utilization factor f ′ at the time of field weakening control can be expressed by the following equation (11) by substituting these equations (9) and (10) into the above equation (5).

Here, in order to prevent the occurrence of voltage saturation, the d-axis current command value Id * is set so that the expected voltage utilization factor f ′ at the time of field weakening control is not more than a predetermined value f0 corresponding to the voltage saturation limit. Just calculate.

  Therefore, first, the following equation (12) is obtained by subtracting the equation (11) from the above equation (1).

Then, the equation (8) is obtained by solving the equation (12) for the d-axis current command value Id *.

  As described above, the microcomputer 17 according to the present embodiment, when the estimated expected voltage utilization rate f exceeds the predetermined value f0 corresponding to the voltage saturation limit (f> f0, see FIG. 5, step 204: YES), Based on the above equation (8), the d-axis current command value Id * is calculated (step 205). Then, the current control is executed using the d-axis current command value Id * (and the q-axis current command value Iq *) corresponding to the field weakening current (step 206), thereby suppressing the occurrence of voltage saturation and improving the efficiency. It is possible to control well.

  In step 204, if the expected voltage utilization rate f does not exceed the predetermined value f0 (f ≦ f0, step 104: NO), the microcomputer 17 sets the d-axis current command value Id * to “Id * = 0 "is calculated (step 207). Then, by performing current control at “Id * = 0”, the field weakening control as described above is not executed.

  As described above, according to the present embodiment, as in the first embodiment, from the transient stage leading to voltage saturation, the occurrence of the voltage saturation is prevented in advance, and the motor current is always performed without performing the voltage limiting process. Can be controlled. As a result, generation of torque ripple and noise can be effectively suppressed. In addition, it is possible to avoid a decrease in torque associated with a decrease in the current command value, thereby maintaining high output performance even in the voltage saturation region.

(Third embodiment)
Hereinafter, a third embodiment in which the present invention is embodied in an electric power steering apparatus (EPS) will be described with reference to the drawings.

  The main difference between this embodiment and the first and second embodiments is only the configuration of the current command value calculation unit and the mode of voltage saturation prevention control. For this reason, for convenience of explanation, the same parts as those in the first and second embodiments are denoted by the same reference numerals, and the explanation thereof is omitted.

  As shown in FIG. 6, the current command value calculation unit 52 of the present embodiment includes a q-axis current command value correction calculation unit 31 that corrects the q-axis current command value Iq * to prevent the occurrence of voltage saturation. In addition, a d-axis current command value calculation unit 43 that calculates a d-axis current command value Id * for executing field weakening control is provided. Then, the current command value calculation unit 52 of the present embodiment, based on the expected voltage usage rate f estimated by the expected voltage usage rate calculation unit 32, performs field weakening control and current command value (q The shaft current command value Iq *) is reduced.

  Specifically, in the d-axis current command value calculation unit 43 of the present embodiment, the expected voltage usage rate f estimated by the expected voltage usage rate calculation unit 32 corresponds to the field weakening control represented by the following equation (13). When a possible limit value, that is, a limit voltage utilization rate fmax is exceeded (f> fmax), the field weakening current (d-axis current command value Id *) is calculated by the following equation (14).

The q-axis current command value correction calculation unit 31 performs the correction process for the q-axis current command value Iq * only when the expected voltage utilization rate f exceeds the limit voltage utilization rate fmax (f> fmax). Run.

  That is, there is a limit to the d-axis current that functions as a field weakening current, and even if a d-axis current command value Id * exceeding the limit is used, the effect of suppressing voltage saturation cannot be obtained. Specifically, in order to establish the calculation formula of the field weakening current (d-axis current command value Id *) shown in the above equation (8), that is, to have a real solution, the numerator “ √ ”must be“ 0 or more ”. The range of the expected voltage utilization rate f that satisfies this condition is the range shown in the following equation (15), and the upper limit value is the limit voltage utilization rate fmax.

In this embodiment, when the expected voltage utilization rate f exceeds the limit voltage utilization rate fmax (f> fmax), the q-axis current command value correction calculation unit 31 is based on the following equations (16) and (17). To calculate a new q-axis current command value Iq **.

That is, these equations (16) and (17) are obtained by substituting the above equation (14) into the above equation (11) and further solving for the q-axis current command value Iq * (Iq **) as “f ′ = f0”. Can be obtained. In the present embodiment, by performing current control based on the new q-axis current command value Iq ** obtained thereby, the expected voltage utilization factor f is set to a voltage in a wider area as shown in FIG. The configuration is such that it can be suppressed to a predetermined value f0 or less corresponding to the saturation limit.

Next, a processing procedure of voltage saturation prevention control in the present embodiment configured as described above will be described.
Note that the processing in steps 301 to 304 in the flowchart of FIG. 8 shown below is the same as the processing in steps 101 to 104 shown in the flowchart of FIG.

  As shown in the figure, the microcomputer 17 of the present embodiment determines that the estimated expected voltage utilization rate f exceeds a predetermined value f0 corresponding to the voltage saturation limit (f> f0, step 304: YES), then The limit voltage utilization factor fmax is calculated using equation (13) (step 305). Then, it is determined whether or not the expected voltage utilization rate f is equal to or less than the limit voltage utilization rate fmax (step 306). If the expected voltage utilization rate f is equal to or less than the limit voltage utilization rate fmax (f ≦ fmax, step In 306: YES, the field weakening current (d-axis current command value Id *) is calculated based on the above equation (8), as in the second embodiment (step 307). In this case, the correction process for the q-axis current command value Iq * is not executed (Iq ** = Iq *, step 308).

  On the other hand, when the expected voltage utilization rate f exceeds the limit voltage utilization rate fmax in step 306 (f> fmax, step 306: NO), the microcomputer 17 calculates the field weakening current (d-axis current) according to the above equation (14). (Command value Id *) is calculated (step 309). Further, by calculating a new q-axis current command value Iq ** based on the above equations (16) and (17), correction processing (update) of the q-axis current command value Iq * calculated in step 302 is executed. (Step 310).

  In step 304, when the estimated expected voltage utilization rate f is equal to or less than a predetermined value f0 corresponding to the voltage saturation limit (f ≦ f0, step 304: NO), the microcomputer 17 calculates the field weakening current. (Id * = 0, step 311), and the correction process for the q-axis current command value Iq * is not executed (Iq ** = Iq *, step 312).

  As described above, the microcomputer 17 according to the present embodiment switches the calculation mode of each current command value (Id *, Iq **) in the d / q coordinate system according to the estimated expected voltage utilization rate f. Then, current control is executed using each current command value (Id *, Iq **) calculated (corrected) by executing these steps 307 to 311 (step 313).

  As described above, according to the present embodiment, it is possible to prevent the occurrence of voltage saturation in a wider area. In particular, when the expected voltage utilization rate f reaches a limit value that can be dealt with by field weakening control, that is, the limit voltage utilization rate fmax, reduction control of the current command value (q-axis current command value Iq *) is also used. , Can maximize its output performance. That is, in EPS, improvement of basic performance is the most important issue as well as reduction of vibration and noise. And by adopting the above configuration and making the best use of the output performance of the motor 12 as a drive source, it is possible to provide an excellent EPS having both high basic performance and quietness.

In addition, you may change each said embodiment as follows.
In each of the above embodiments, the expected voltage utilization rate calculation unit 32 is provided separately from the q-axis current command value correction calculation unit 31 and the d-axis current command value calculation unit 43, but these are integrated. It is good also as a structure.

In each of the above embodiments, the voltage limiting process is omitted for convenience of explanation, but a configuration in which this is used together may be used.
Furthermore, although not particularly mentioned in the above embodiments, the d-axis current command value Id * may be limited in consideration of the demagnetizing action by the field weakening control.

  In each of the above embodiments, the motor control signal is generated by executing current feedback control. However, the motor control signal may be generated by executing open control.

The schematic block diagram of an electric power steering device (EPS). The control block diagram which shows the electric constitution of EPS in 1st Embodiment. The flowchart which shows the process sequence of the voltage saturation prevention control in 1st Embodiment. The control block diagram which shows the electric constitution of EPS in 2nd Embodiment. The flowchart which shows the process sequence of the voltage saturation prevention control in 2nd Embodiment. The control block diagram which shows the electric constitution of EPS in 3rd Embodiment. Explanatory drawing which shows the aspect of the voltage saturation prevention control in 3rd Embodiment. The flowchart which shows the process sequence of the voltage saturation prevention control in 3rd Embodiment. Explanatory drawing which shows the aspect of a voltage limiting process (voltage saturation guard).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 10 ... EPS actuator, 11 ... EPS ECU, 12 ... Motor, 17 ... Microcomputer, 18 ... Drive circuit, 22, 42, 52 ... Current command value calculating part, 23 ... Motor control signal generation , 31 ... q-axis current command value correction calculation unit, 32 ... expected voltage utilization rate calculation unit, 43 ... d-axis current command value calculation unit, Id * ... d-axis current command value, Iq *, Iq ** ... q-axis Current command value, ω: rotational angular velocity, Vb: power supply voltage, Vmax: maximum voltage, f, f ′: expected voltage utilization rate, f0: predetermined value, fmax: limit voltage utilization rate.

Claims (5)

  1. Motor control device comprising motor control signal generating means for generating a motor control signal by executing current control in a d / q coordinate system, and a drive circuit for outputting three-phase drive power to the motor based on the motor control signal Because
    The motor control signal generation means is an expected voltage utilization rate that is a ratio of a required output voltage to a maximum voltage that can be applied to the drive circuit based on a rotational angular velocity of the motor and a current command value of the d / q coordinate system. And correcting the current command value so that the estimated expected voltage utilization rate does not exceed a predetermined value corresponding to the voltage saturation limit.
  2. The motor control device according to claim 1,
    The motor control signal generating means calculates a d-axis current command value to execute field-weakening control so that the estimated expected voltage utilization rate does not exceed the predetermined value, and the estimated expected voltage utilization rate is When the limit value that can be dealt with by the field weakening control is exceeded, the correction is made so that the expected voltage utilization rate does not exceed the predetermined value by reducing the q-axis current command value together. Motor control device.
  3. The motor control device according to claim 1,
    The motor control device, wherein the motor control signal generating means reduces a q-axis current command value so that the estimated expected voltage utilization rate does not exceed the predetermined value.
  4. The motor control device according to claim 1,
    The motor control signal generating means calculates a d-axis current command value to execute field-weakening control so that the estimated expected voltage utilization rate does not exceed the predetermined value;
    A motor control device.
  5.   An electric power steering device comprising the motor control device according to any one of claims 1 to 4.
JP2008214393A 2008-08-22 2008-08-22 Motor control device and electric power steering device Expired - Fee Related JP5292995B2 (en)

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JP2008214393A JP5292995B2 (en) 2008-08-22 2008-08-22 Motor control device and electric power steering device
CN2009801194177A CN102047552B (en) 2008-08-22 2009-08-20 Motor control device and electric power steering device
PCT/JP2009/064547 WO2010021353A1 (en) 2008-08-22 2009-08-20 Motor control device and electric power steering device
US12/990,687 US8686672B2 (en) 2008-08-22 2009-08-20 Motor control device and electric power steering device
EP09808289.4A EP2317642A4 (en) 2008-08-22 2009-08-20 Motor control device and electric power steering device

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WO2010021353A1 (en) 2010-02-25
US20110127934A1 (en) 2011-06-02
CN102047552B (en) 2013-12-18
CN102047552A (en) 2011-05-04
JP2010051125A (en) 2010-03-04

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